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Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media.

News Release Number: STScI-2002-18

Hubble Discovers Black Holes in Unexpected Places

September 17, 2002: Medium-size black holes actually do exist, according to the latest findings from NASA's Hubble Space Telescope, but scientists had to look in some unexpected places to find them. The previously undiscovered black holes provide an important link that sheds light on the way in which black holes grow. Even more odd, these new black holes were found in the cores of glittering, "beehive" swarms of stars called globular star clusters, which orbit our Milky Way and other galaxies. The black hole in globular cluster M15 [left] is 4,000 times more massive than our Sun. G1 [right], a much larger globular cluster, harbors a heftier black hole, about 20,000 times more massive than our Sun.

Q & A: Understanding the Discovery

1.
Where are the globular star clusters that harbor these medium-size black holes?

Astronomers uncovered one of the black holes in the center of the globular star cluster M15, 32,000 light-years away in the constellation Pegasus. The black hole is 4,000 times more massive than our Sun. A 20,000-solar-mass black hole was found in the giant globular cluster G1, located 2.2 million light-years away in the neighboring Andromeda galaxy.

2.
What is the significance of this discovery?

Astronomers have discovered another home for black holes. Black holes also live in the cores of most galaxies. But those are called supermassive black holes.

The new findings also promise a better understanding of how galaxies and globular clusters first formed billions of years ago. Globular star clusters contain the oldest stars in the universe. If globular clusters have black holes now, then they most likely had black holes when they formed billions of years ago. So, black holes may be even more common in the universe than previously thought.